O2 Group Research Articles

Beneficial effect of reduced oxygen concentration with transfer of blastocysts in IVF patients older than 40 years old

The aim of the present study was to determine the impact of oxygen concentration on implantation, pregnancy and delivery rates in IVF patients older than 40 year old with transfer of blastocysts. Included were 558 women aged 23-45 years old undergoing IVF/ICSI procedures whose embryos were cultured at blastocyst stage under two different oxygen environments (a bi-gas system: 5.6% CO2 in air and a tri-gas system: 5.6% CO2, 5% de O2 and 89.4% N2). The main outcome measures of this study are implantation, pregnancy and delivery rates. Implantation, pregnancy and delivery rates are found to be reduced in women older than 40 years old. The implantation and pregnancy rates are significantly higher in women older than 40 years old from the 5% of O2 group, in comparison to the 20% group (25.00% versus 2.70% and 41.38% versus 5.56%; P < 0.05). The deliveries rates were 13.79% and 5.56% in the 5% and 20% oxygen groups respectively (P: NS). The birthweight was similar in both study groups (P: NS). Gestational age was significantly longer in wo- men from the 5% of O2 group, in comparison to the 20% (36.87 versus 35.87 weeks, P < 0.05). Results indicated that the embryonic culture with 5% of oxygen and transfer of blastocysts in women older than 40 years old improve the results in the in Vitro fertilization/intracytoplasmic injection procedures (IVF/ICSI).

O2 Activation in a Dinuclear Fe(II)/EDTA Complex: Spin Surface Crossing As a Route to Highly Reactive Fe(IV)oxo Species

We study the cleavage of O2 in gas phase [(EDTAH)Fe(O2)Fe(EDTAH)]2-, a proposed intermediate in the aqueous Fe(II)-to-Fe(III) autoxidation reaction in the presence of atmospheric dioxygen and EDTA ligand. The role of the exchange coupling between the locally high-spin Fe centers in the O-O dissociation is investigated. Using results from broken symmetry (BS) density functional theory (DFT) calculations, we show that the system can be modeled as two high-spin (HS) S = 5/2 Fe(III) d5 centers coupled through a bridging peroxo O2(2-) ligand, consistent with hypotheses advanced in the literature. We show that in this electronic configuration the O-O cleavage reaction is forbidden by (spin) symmetry. Dissociation of the O2(2-) group to the product ground state may only take place if the system is allowed to undergo a transition to a state of lower spin multiplicity (S = 4) as the O-O bond is stretched. We show that the exchange coupling between the two Fe ions in [(EDTAH)Fe(O2)Fe(EDTAH)]2- plays only a minor role in defining the chemistry of O2 activation in this system. The peroxo/oxo interconversion involves a state outside the Heisenberg spin ladder of the initial S = 5 state. In this S = 4 state, the dinuclear complex evolves to two oxo complexes, [EDTAH x Fe(IV)O]-, with an overall energy barrier of only approximately 86 kJ mol(-1). According to recent theoretical work, the latter species are exceptionally strong oxidants, making them ideal candidate catalysts for organic oxidations (including C-H bond hydroxylation). We highlight the (spin) symmetry forbidden nature of the reaction on the S = 5 surface and its symmetry allowed character in the electronic configuration with S = 4.

Effects of prolonged oxygen exposure at different concentrations on expressions of vascular endothelial growth factor and its receptors mRNA in pulmonary tissues of neonatal rat

Objective To study the effects of prolonged oxygen exposure at different concentrations on expressions of vascular endothelial growth factor (VEGF) and its receptors (VEGF receptor-1 ,VEGFR1 and VEGF receptor-2, VEGFR2)mRNA in lungs of neonatal rat. Methods Thirty-two SD rat pups were randomly divided into control and experimental group. Rats in the experimental group were further divided into three subgroups: 30% O2, 50% O2 and 75% O2 group. Each group had 8 rats. The rats were ,sacrificed at postnatal day 21 and their right lower lobes were collected. Expressions of VEGF, VEGFR1 and VEGFR2 mRNA were detected by RT-PCR. Results There was no effect on VEGF, VEGFR1 or VEGFR2 mRNA expression in 30% O2 group. The expressions of VEGF mRNA in the 75% O2 group was 0. 48 times of the control (P<0. 05). The expressions of VEGFR1 mRNA(P<0.01) and VEGFR2 mRNA (P<0.01) in 50% O2 and 75% O2 group were lower than those of control. Condusions Prolonged exposure to moderate or high oxygen concentration may reduce the expression of VEGF and its receptors' mRNA in the lung tissues of neonatal rats. Key words: Vascular endothelial growth factor As Vascular endothelial growth factor receptor-1; Vascular endothelial growth factor receptor-2; Oxygen inhalation therapy; Oxygen; Rats

Nimodipine Prevents Transient Cognitive Dysfunction After Moderate Hypoxia in Adult Mice

Cognitive changes associated with moderate hypoxia may be related to the elevation of cytosolic calcium (Ca) levels which may, in turn, affect neurotransmitter synthesis and metabolism. We tested whether treatment with nimodipine (NIMO), an L-type Ca channel blocker, would preserve working memory after hypoxic hypoxia. We randomized 157 Swiss-Webster, 30 to 35 g mice (6 to 8 wk) to 6 groups, which were exposed to the following gas mixtures for 1 hour: (1) O2 21%; (2) O2 21% followed by 0.1 mg/kg of subcutaneous NIMO; (3) O2 21% followed by vehicle (60% polyethylene glycol/40% methanol); (4) O2 10%; (5) O2 10% then NIMO; (6) O2 10% then vehicle. The Object Recognition Test (ORT) was given once either on Day 1 or Day 7 to assess changes in short-term memory. ORT exploits the tendency of mice to prefer novel over familiar objects. Two identical objects were placed in an arena for 15 minutes of training. During the testing 1 hour later, one of the objects was replaced by a new object. Recognition Index (RI) was used to compare performance. It is defined as the time spent exploring the novel object divided by the time spent exploring both objects, the novel plus the familiar, and this ratio is converted to a percentage. RI was analyzed with analysis of variance. Tukey Honestly Significant Difference tests were used for post hoc comparisons when appropriate. P values <0.05 were considered significant. RI for the control group was 68.3% (SE+/-3.6%). RI was 53.7% (SE+/-3.8%) for the 10% O2 group on the first posttreatment day. O2 saturation (SpO2) for the hypoxic group was 71.7% (SE+/-0.5%). By Day 7, RI for the 10% O2 group increased to 64.2% (SE+/-4.7%), which was not significantly different from control. On Day 1, RI was 68.6% (SE+/-5.2%) for hypoxic rodents treated with NIMO. These results were statistically significant. Low RI indicates impaired working memory and high RI indicates intact working memory. These results suggest that NIMO prevented impairment of working memory after moderate hypoxia. NIMO reverses the disturbance of short-term working memory caused by moderate hypoxia in mice. The results may have implications for cognitive changes linked to Ca homeostasis in the postoperative period.

250 EFFECT OF LOW OXYGEN TENSION ATMOSPHERE AND MATURATION MEDIA ON IN VITRO-MATURED SWINE OOCYTES

The aim of this study was to evaluate the efficiency of a low oxygen tension atmosphere (5% CO2, 5% O2, and 90% N2) on swine oocyte maturation in chemically defined media or when supplemented with porcine follicular fluid (PFF). Briefly, oocytes were in vitro matured for 44 h in TCM-199 with 10% PFF or 0.1% PVA added, under a low oxygen tension atmosphere or a normal oxygen tension atmosphere (5% CO2 in air, approximate 20% O2). At 0 and 44 h of maturation, cumulus oophorus cells were removed. To evaluate the migration of cortical granules, oocytes were fixed, permeabilized, and incubated in 100 μg of FITC-PNA mL–1 for 30 min. Oocytes were then incubated in 10 μg mL–1 of Rnase for 30 min and in 10 μg mL–1 of propidium iodide for 10 min to verify nuclear maturation by confocal microscopy (Zeiss LSM 510 Meta). Heat shock protein 70 (HSP70) content was assessed as described in Kawarsky and King (2001 Zygote 9(3), 39–50) to verify oxidative stress. Data were analyzed by the SAS System for Windows (2000). The nonparametric ANOVA NPAR1WAY procedure was applied to evaluate nuclear maturation rate by comparing groups in pairs. Migration of cortical granules and HSP70 content were analyzed using PROC GLM (LSD test of means). The effects of treatment and manipulation were verified in all analyses. The significance level was 5%, and data were presented as means ± SEM. Results indicated that the percentage of metaphase II oocytes did not differ among groups after 44 h of maturation [PFF 5% O2 (89.16 ± 3.73a), PFF 20% O2 (86.59 ± 6a), PVA 5% O2 (79.62 ± 8.22a), and PVA 20% O2 (93 ± 5.17a)]. However, these groups were different from the 0-h group (0 ± 0b). Results for the percentage of cortical granule migration showed that 0-h oocytes (38.92 ± 2.75a) had lower migration rates compared with other groups. After 44 h of maturation, migration of the cortical granule rate of the PFF-supplemented group under a 5% O2 atmosphere (61.66 ± 3.21b) was different when compared with the PVA 20% O2 group (50.97 ± 3.48c). The other groups showed intermediate results, but without statistical differences [PFF 20% O2 (58.51 ± 2.5bc) and PVA 5% O2 (53.75 ± 3.14bc)] for the migration of cortical granules. Moreover, no difference at pixel quantification of HSP70 was observed among groups after 44 h of maturation [PFF 5% O2 (116.45 ± 40.94a), PFF 20% O2 (44.44 ± 12.66a), PVA 5% O2 (29.95 ± 7.95a), and PVA 20% O2 (58.49 ± 22.2a)], although these groups were different from the 0-h group (247.41 ± 38.59b). Although the HSP content decreased throughout in vitro maturation of swine oocytes under the low and high oxygen tension atmospheres, it can be concluded that a low oxygen tension atmosphere did not affect nuclear maturation and rates of cortical granule migration regardless of maturation media supplementation. Financial support: FAPESP (grant no. 05/01420-7).

Effect of sevoflurane postconditioning on spinal cord ischemia reperfusion injury via the release of oxygen free radicals in rabbits

To investigate whether postconditioning with sevoflurane could alleviate spinal cord ischemia reperfusion injury in rabbits, and whether the beneficial effect is dependent on oxygen free radicals. In Experiment 1, 48 male New Zealand white rabbits were randomly assigned to six groups (n=8 each). Animals in the sham group only underwent sham-operation. Animals in the control group underwent spinal cord ischemia for 20 min without postconditioning. Animals in 02 postconditioning group (Group O2) inhaled 100% O2 from 5 min before reperfusion and lasted 13 min. Animals in sevoflurane postconditioning groups (Group Sevo0.5, Sevo1.0 and Sevo1.5) inhaled 0.5, 1.0, 1.5 minimum alveolar concentration (MAC) sevoflurane in 100% O2 from 5 min before reperfusion and lasted 10 min, then inhaled 100% O2 for 3 min to wash out the remaining sevoflurane. In Experiment 2, 36 male New Zealand White rabbits were randomly assigned to four groups (n=9 each). Animals in O2 and Sevo groups received normal saline (5 ml/kg intravenously) 1 h before postconditioning with 100% O2 and 1.0 MAC sevoflurane, respectively. In the DMTU + Sevo and DMTU + O2 groups, 5 ml/kg of 10% dimethylthiourea (DMTU, a potent oxygen free radical scavenger, dissolved in saline) was administered intravenously at the same time. Spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, hind-limb motor function and histopathology of the spinal cord were examined in a blinded fashion. (1) The neurologic and histopathologic outcomes in the sevoflurane postconditioning groups were better than those in the control group (P < 0.05), the histopathologic outcomes in Sevo1.0 group were better than that in Sevo0.5 and Sevo1.5 groups (P < 0.05). (2) The neurologic and histopathologic outcomes in Sevo, DMTU + Sevo and DMTU + O2 groups were better than those in the O2 group (P < 0.05), the histopathologic outcomes in Sevo group were better than that in the DMTU + Sevo and DMTU + O2 groups (P < 0.05). Our study demonstrates that sevoflurane postconditioning against spinal cord ischemia injury via the release of oxygen free radicals in rabbits.

Preliminary study among truck drivers in Turkey: Effects of ultraviolet light on some skin entities

In this study, we aimed to compare driver (left) and opposite (right) sides for some skin entities in drivers. We also evaluated the effect of occupational duration, age and skin type among this population. One hundred and forty-eight truck drivers were included in this study. Sun exposed areas were classified. Dermatological entities such as actinic keratosis, solar lentigo, seborrheic keratosis, melanocytic nevus, spider angioma, ephelid, basal cell carcinoma (BCC), squamous cell carcinoma, and melanoma were compared to driver and right sides. In addition, drivers were divided into two subgroups according to: (i) age (subgroups A1, 20-40 years, and A2, >40 years); (ii) occupational duration (subgroups O1, 1-10 years, and 02, >10 years); and (iii) skin type (subgroups S1, skin types I and II, and S2, skin types III and IV. Each of the two subgroups were compared with respect to the total prevalence (left and right sides) of lesions excluding the location. Seborrheic keratosis and lentigo solaris were found to be increased on the driver side of the face (P = 0.00) and ear (P = 0.013), respectively. Statistically significant increases of lesions on the driver side were determined according to the subgroups: melanocytic nevi were found to be increased on the driver side in A1 (P = 0.00), A2 (P = 0.00), O2 (P = 0.00), S1 (P = 0.00) and S2 (P = 0.006) groups; actinic keratoses were found to be significantly increased on the driver side in A2 and O2 groups (P = 0.03 for both).

Molecular dynamics study of Pseudomonas aeruginosa lectin‐II complexed with monosaccharides

We present the results of a series of 10-ns molecular dynamics simulations on Pseudomonas aeruginosa lectin-II (PA-IIL) and its complexes with four different monosaccharides. We compare the saccharide-free, saccharide-occupied, and saccharide- and ion-free forms of the lectin. The results are coupled with analysis of the water density map and calcium coordination. The water density pattern around the binding site in the free lectin molecular dynamics was fitted with that in the X-ray and with the hydroxyl groups of the monosaccharide within the lectin/monosaccharide complexes and the best ligand was predicted based on the best fit. Interestingly, the water density pattern around the binding site in the uncomplexed lectin exactly fitted the O2, O3, and O4 hydroxyl groups of the fucose complex with the lectin. This observation could lead to a hypothesis that the replacement of these three water molecules from the binding site by the monosaccharide decreases the entropy of the complex and increases the entropy of the water molecules, which favors the binding. It suggests that the high density peaks of the solvent around the binding site in the free protein could be the tool to predict hydroxyl group orientation of the sugar in the protein/sugar complexes. The high affinity of PA-IIL binding site is also attributed to the presence of two calcium ions, each of them making five to six coordinations with the protein part and two coordinations with either water or the monosaccharide. When the calcium ions are removed from the simulated system, they are replaced by sodium ions from the solvent. These observations rationalize the high binding affinity of PA-IIL towards fucose.

Understanding the Structural Basis for Substrate and Inhibitor Recognition in Eukaryotic GH11 Xylanases

Endo-β1,4-xylanases (xylanases) hydrolyse the β1,4 glycosidic bonds in the backbone of xylan. Although xylanases from glycoside hydrolase family 11 (GH11) have been extensively studied, several issues remain unresolved. Thus, the mechanism by which these enzymes hydrolyse decorated xylans is unclear and the structural basis for the variation in catalytic activity within this family is unknown. Furthermore, the mechanism for the differences in the inhibition of fungal GH11 enzymes by the wheat protein XIP-I remains opaque. To address these issues we report the crystal structure and biochemical properties of the Neocallimastix patriciarum xylanase NpXyn11A, which displays unusually high catalytic activity and is one of the few fungal GH11 proteins not inhibited by XIP-I. Although the structure of NpXyn11A could not be determined in complex with substrates, we have been able to investigate how GH11 enzymes hydrolyse decorated substrates by solving the crystal structure of a second GH11 xylanase, EnXyn11A (encoded by an environmental DNA sample), bound to ferulic acid-1,5-arabinofuranose-α1,3-xylotriose (FAX 3). The crystal structure of the EnXyn11A–FAX 3 complex shows that solvent exposure of the backbone xylose O2 and O3 groups at subsites −3 and +2 allow accommodation of α1,2-linked 4-methyl- D-glucuronic acid and L-arabinofuranose side chains. Furthermore, the ferulated arabinofuranose side chain makes hydrogen bonds and hydrophobic interactions at the +2 subsite, indicating that the decoration may represent a specificity determinant at this aglycone subsite. The structure of NpXyn11A reveals potential −3 and +3 subsites that are kinetically significant. The extended substrate-binding cleft of NpXyn11A, compared to other GH11 xylanases, may explain why the Neocallimastix enzyme displays unusually high catalytic activity. Finally, the crystal structure of NpXyn11A shows that the resistance of the enzyme to XIP-I is not due solely to insertions in the loop connecting β strands 11 and 12, as suggested previously, but is highly complex.

Effectiveness of colorectal laparoscopic surgery on patients at high anesthetic risk: an intervention cohort study

The aim of the study was to assess the effectiveness of laparoscopic colorectal surgery in patients at high preoperative anesthetic risk because of associated pathologies. From January 2003 until January 2005, 116 patients were systematically assigned at a ratio of 1:1 to one of two groups: laparoscopy surgery (n=59, of which 31 were American Society of Anesthesiologists score [ASA] I-II [L1] and 28 ASA III-IV [L2]) or open surgery (n=57, of which 30 were ASA I-II [O1] and 27 ASA III-IV [O2]). Data on patient demographics and clinical and anesthetic variables were collected prospectively. Informed consent was obtained from the patients, and approval was obtained from the designated review board of the institution involved. The number of minor anesthetic complications during surgery was higher in L2 patients. No differences were observed in blood gas parameters studied during surgery (pCO(2), pH, and pO(2)/FiO(2)). Transfusion rates in the laparoscopy group at greater anesthetic risk (L2) were lower than those of the high-risk conventional surgery group (O2; 21.4 vs 63%, P<0.02). Duration of stay in the surgical recovery room and the inpatient ward were also shorter in the L2 group than in the O2 group (8.7+/-4.5 vs 12.2+/-6 days, P=0.02). There was no difference in perioperative clinical variables between laparoscopy groups (L1, L2). Postoperative recovery of ASA III-IV patients is better after laparoscopic surgery for colorectal cancer, at the expense of a higher rate of minor anesthetic occurrences during surgery.

Low oxygen tension and euploidy after preimplantation genetic screening

In 2002 Bean and colleagues suggested a higher rate of mitotic non-disjunction in 5% CO2 in air. However when cultured in a 5% oxygen (O2) concentration the rate of mitotic induced mosaicism returned to the in vivo control models. The purpose of this study is to determine if the introduction of reduced O2 culture microenvironment would yield a higher rate of euploidy in preimplantation genetic screening (PGS) patients. Prospective cohort study of PGS patients where embryos were cultured in a 20% O2 and 5% O2 microenvironment. Embryos were cultured individually in a Sage sequential culture medium in 6% CO2 and air or lowered O2 (5%) balanced with nitrogen. On day 3 embryos >4 cells were subjected to biopsy of one cell in a Sage Ca/Mg free medium. The rate of blastocyst formation was evaluated in the two culture systems. Euploidy was determined from the reference laboratory report as normal or abnormal. Additionally, the rate of blastocyst formation was evaluated for euploid and aneuploid embryos. A total of 933 embryos were subjected to embryo biopsy on day 3 post insemination. Where 456 embryos were biopsied and cultured in the low (5%) O2 group and 477 embryos in the elevated (20%) O2. In the low oxygen microenvironment there was no significant (P=0.27) increase in the rate of euploidy in embryos as determined by FISH. There was a euploidy rated of 152/456 (33%) in low O2 and 143/477 (30%) in the CO2 in air culture system (not significant). In the low O2 culture system there was a significantly (P=0.004) higher rate of blastocyst formation for euploidy embryos in the low O2 as compared to elevated O2. Euploid embryos developed to blastocyst at a rate of 115/152 (76%) in low O2 vs. 86/143 (43%) in elevated O2. Where as aneuploid embryos in the low O2 vs. the elevated O2 was 141/304 (46%) and 138/334 (41%) respectively (not significant). Results show there was no decrease in mitotic non-disjunction in the human with variable oxygen tensions on the embryo. Interestingly we did show there were significantly more euploid blastocysts available for transfer when culturing in a lower O2 environment. Additionally, there was no significant increase in aneuploid embryos that developed to the blastocyst stage in low O2 vs. higher oxygen levels. Therefore showing there is an advantage to culturing embryos in low O2 in order to yield the highest number of good quality embryos available for embryo transfer.

Development and quality of porcine embryos in different culture system and embryo-producing methods

In this study, the developmental ability and cellular composition of porcine IVF, parthenote and somatic cell nuclear transfer (SCNT) embryos were evaluated following different in vitro culture systems. Group 1, embryos were cultured in NCSU-23 with 5.55 mM D-glucose (NCSU+) until day 6 on 20% O(2) or 5% O(2) (Group 2). Group 3, embryos were cultured in D-glucose-free NCSU-23 (NCSU-) with 0.17 mM Na pyruvate/2.73 mM Na lactate for 58 h and subsequently cultured in NCSU+ until day 6 (NCSU -/+) on 20% O2 or 5% O(2) (Group 4). IVF blastocysts did not differ significantly with O(2) concentrations, but differed significantly with major energy source (glucose and pyruvate/lactate). In Group 3 and 4 IVF blastocysts, the total cell number and apoptosis rates were not significantly different with different O(2) concentrations. Blastocyst rate, total cell number and apoptosis rate in Groups 3 and 4 parthenote embryos also were not significantly different. Parthenote and SCNT, under the same culture treatment, exhibited significant differences in blastocyst and apoptosis rates (47.5 +/- 16.1 vs. 24.0 +/- 4.0 and 4.9 +/- 9.0 vs. 22.8 +/- 23.3). Apoptosis-generating rate increased in the order parthenote, IVF and then SCNT. In conclusion, in vitro development of porcine embryos was not affected by O(2) concentrations but was affected by major energy source. Even so, the concentration of each major energy source and the timing of its inclusion in culture could accomplish relatively high embryonic development, the apoptosis rate stressed that more work still needs to be done in developing a better defined culture system that could support SCNT embryos equivalent to in vivo preimplantation porcine embryos.

Revealing regioselectivity in hydrogenation of 1-phenyl-1,2-propanedione on Pt catalysts

Adsorption of 1-phenyl-1,2-propanedione ( A), a widely studied molecule in heterogeneously catalyzed enantioselective hydrogenation, and 2,3-hexanedione on a Pt(111) surface was studied using density functional theory. A cluster consisting of two slabs and 31 Pt atoms was used as a model for the catalyst. The results revealed the origin of observed regioselectivity in the hydrogenation of carbonyl groups C1 O1 and C2 O2 of A and the lack of regioselectivity in the case of 2,3-hexanedione on Pt catalysts. The adsorption modes of A in which the C1 O1 carbonyl group next to the phenyl ring is activated toward hydrogenation ( η C 1 O 1 2 adsorptions) are more stable than the corresponding adsorption modes where the C2 O2 group is activated ( η C 2 O 2 2 adsorption). This indicates that the catalyst surface is covered mainly by reaction intermediates leading to the hydrogenation of the carbonyl group C1 O1 and eventually regioselectivity, presuming that the hydrogenation rates of C1 O1 and C2 O2 are of the same order of magnitude. The adsorption energy of 2,3-hexanedione does not depend on which of the carbonyl groups is adsorbed as η 2 -mode, and thus the hydrogenation on Pt is not regioselective, as has been observed experimentally. Thus the regioselectivity in the hydrogenation of A and 2,3-hexanedione can be explained by the interactions between the substrate and the metal surface.

Isoflurane Produces Delayed Preconditioning against Spinal Cord Ischemic Injury via Release of Free Radicals in Rabbits

Whether isoflurane preconditioning produces delayed neuroprotection in the spinal cord is unclear. The authors tested the hypothesis that isoflurane produces delayed preconditioning against spinal cord ischemic injury and, further, that the beneficial effect is dependent on free radicals. In experiment 1, 63 rabbits were randomly assigned to seven groups (n = 9 each): Animals in the control group only underwent spinal cord ischemia without pretreatment; animals in the Iso24h, Iso48h, and Iso72h groups received 40 min of 1.0 minimum alveolar concentration isoflurane in 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia; animals in the O2 24h, O2 48h, and O2 72h groups received 40 min of 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia. In experiment 2, 48 rabbits were randomly assigned into four groups (n = 12 each): Animals in the O2 and Iso groups received 3 ml/kg saline intraperitoneally 1 h before each session of oxygen pretreatment and isoflurane pretreatment, respectively. In the DMTU+Iso and DMTU+O2 groups, 10% dimethylthiourea (DMTU, a potent free radical scavenger) dissolved in saline (3 ml/kg) was administered at the same time point. Twenty-four hours after the last pretreatment, animals were subjected to spinal cord ischemia. Spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, neurologic function and histopathology of the spinal cord were examined. In experiment 1, the neurologic and histopathologic outcomes in the Iso24h and Iso48h groups were better than those in the control group (P < 0.005 for each comparison); the neurologic and histopathologic outcomes in the control group showed no significant differences in comparison with the O2 24h, O2 48h, O2 72h, and Iso72h groups (P > 0.05 for each comparison). In experiment 2, the neurologic and histopathologic outcomes in the Iso group were better than those in the DMTU+Iso, O2, and DMTU+O2 groups (P < 0.01 for each comparison); there were no significant differences in the neurologic and histopathologic outcomes among the DMTU+Iso, O2, and DMTU+O2 groups (P > 0.05 for each comparison). Isoflurane produces delayed preconditioning against spinal cord ischemic injury, and the beneficial effect may be dependent on the release of free radicals.

Effects of Inhalation of Oxygen on Free Radical Metabolism and Oxidative, Antioxidative Capabilities of the Erythrocyte After Intensive Exercise

Two groups, each containing 10 young healthy male students, participated in the study. One group breathed 70% O2 after exercise (70% O2 group) while the other group breathed normal air (Normal air group) after exercise. The results of the study show the following: (1) in both groups, the Monodehydyoxygenbate (MDA) in erythrocyte (RBC) and serum, and superoxide dismutase (SOD) and glutathione Peroxidas (GSH-px) in serum were significantly higher immediately after exercise than at rest; (2) the MDA in RBC and serum were significantly higher in the Normal air group than in the 70% O2 group for 30 minutes after exercise; and (3) the SOD in serum and GSH-px in blood and serum were significantly higher in the 70% O2 group than in the Normal air group for 30 minutes after exercise. We suggest that the effects of inhaling 70% O2 could prevent fatigue from antagonizing free radicals damage, hastening removal of free radicals, which would facilitate recovery from fatigue.

Ventilatory response to hypercapnia and hypoxia after extensive lesion of medullary serotonergic neurons in newborn conscious piglets

Acute inhibition of serotonergic (5-HT) neurons in the medullary raphé (MR) using a 5-HT(1A) receptor agonist had an age-dependent impact on the "CO(2) response" of piglets (33). Our present study explored the effect of chronic 5-HT neuron lesions in the MR and extra-raphé on the ventilatory response to hypercapnia and hypoxia in piglets, with possible implications on the role of 5-HT in the sudden infant death syndrome. We established four experimental groups. Group 1 (n = 11) did not undergo any treatment. Groups 2, 3, and 4 were injected with either vehicle or the neurotoxin 5,7-dihydroxytryptamine in the cisterna magna during the first week of life (group 2, n = 9; group 4, n = 11) or second week of life (group 3, n = 10). Ventilation was recorded in response to 5% CO(2) (all groups) and 12% O(2) (group 2) during wakefulness and sleep up to postnatal day 25. Surprisingly, the piglets did not reveal changes in their CO(2) sensitivity during early postnatal development. Overall, considerable lesions of 5-HT neurons (up to 65% decrease) in the MR and extra-raphé had no impact on the CO(2) response, regardless of injection time. Postlesion raphé plasticity could explain why we observed no effect. 5,7-Dihydroxytryptamine-treated males, however, did present a lower CO(2) response during sleep. Hypoxia significantly altered the frequency during sleep in lesioned piglets. Further studies are necessary to elucidate the role of plasticity, sex, and 5-HT abnormalities in sudden infant death syndrome.

Randomized clinical trial to evaluate the effects of perioperative supplemental oxygen administration on the colorectal anastomosis

Perioperative supplemental oxygen therapy may have beneficial effects on wound healing following colorectal surgery. The aim of this study was to evaluate the effects of such therapy on colorectal anastomotic pH and partial pressure of carbon dioxide (PCO(2)) gap. Forty-five patients undergoing anterior resection for rectal or sigmoid cancer were randomized to receive 30 or 80 per cent perioperative oxygen. Administration was commenced after induction of anaesthesia and maintained for 6 h after surgery. Intragastric and anastomotic tonometric catheters were placed in each patient and intramucosal pH (pHi) was measured immediately after operation, and 6 and 24 h later. Gastric and anastomotic pHi and PCO(2) gap in each group were compared. There was a significantly lower anastomotic pHi and wider PCO(2) gap for gastric readings in the 30 per cent O(2) group, both 30 min (pHi, P = 0.006; PCO(2) gap, P = 0.006) and 6 h (pHi, P = 0.024; PCO(2) gap, P = 0.036) after surgery. There were no differences 24 h after surgery while breathing room air (pHi, P = 0.131; PCO(2) gap P = 0.139). No difference was found between gastric and anastomotic readings at any time point in the 80 per cent O(2) group. Perioperative administration of 80 per cent O(2) both during surgery and for 6 hours afterwards is associated with an improvement in relative anastomotic hypoperfusion as assessed by the measurement of pHi and PCO(2) gap.

The Effect of Reducing Target Oxygen Saturation Levels on the Risk of Severe Retinopathy of Prematurity

Background: Previous studies have shown that a reduction in target oxygen saturation levels to 85 to 93% reduces the risk of severe retinopathy of prematurity (ROP). The effect on ROP risk of a more modest reduction in target oxygen saturation levels is unknown. Methods: At the beginning of 2004, one neonatal intensive care unit instituted new oxygen saturation guidelines that changed target levels from the upper 90s to 90 to 96%. A retrospective cohort study was done to determine the risks for right eyes only of (1) threshold or type I prethreshold and (2) stage 3. These risks were compared between two groups of all eligible infants born up to 10 months before (higher O2 group, n= 45) and up to 16 months after (lower O2 group, n= 60) the policy change. Logistic regression was used to calculate relative risks adjusted for birth weight, gestational age, apnea, days of mechanical ventilation, and length of hospital stay. Results: The risk of threshold or type I prethreshold ROP was 18% (8/45) in the higher O2 group versus 13% (8/60) in the lower O2 group (adjusted relative risk= 0.68, 95% CI= 0.30, 1.53). The risk of stage 3 ROP was 27% in the higher O2 group and 22% in the lower O2 group (adjusted relative risk= 0.76, 95% CI= 0.41, 1.40). Conclusion: These data suggest that even a modest reduction in target oxygen saturation levels to 90 to 96% in the first several weeks of life reduces the risk of severe retinopathy of prematurity.

Reduced Liver Apoptosis After Venous Systemic Oxygen Persufflation in Non-Heart-Beating Donors

Graft injury caused by warm ischemia in livers from non-heart-beating donors (NHBDs) strongly affects posttransplantation outcome and is associated with liver apoptosis, which is mediated by death receptors, such as Fas, a surface receptor of the tumor necrosis factor (TNF)-α family. The aim of this study was to test the ability of venous systemic oxygen persufflation (VSOP) to reduce apoptotic changes and Fas activation in the liver after warm ischemic insult in vivo. Livers of male Wistar rats were harvested 30 min after cardiac arrest from non-heart-beating donors (NHBD) with (NHBD + O2) or without (NHBD) application of gaseous oxygen during the cold storage period via the suprahepatic caval vein. After 24 h of storage in University of Wisconsin solution at 4°C, viability of the livers was assessed upon isolated reperfusion in vitro. Conventional signs of tissue damage like enzyme release and bile production showed a significantly elevated nonspecific cell injury in the NHBD group. TUNEL staining revealed increased DNA fragmentation of sinusoidal endothelial cells in the NHBD group and more apoptotic hepatocytes than in the control group. All these alterations could be almost abrogated by the use of VSOP in the NHBD + O2 group. The immunohistochemical staining of Fas antigen expression showed a significantly elevated Fas receptor expression in the NHBD and NHBD + O2 groups, in accord with an eightfold increase of Fas receptor mRNA detected by real-time reverse-transcription polymerase chain reaction (RT-PCR). These results demonstrate that the postischemic apoptotic rate of sinusoidal endothelial cells in NHBD livers can be reduced by the use of VSOP. A significant improvement in liver integrity and viability was obtained with this technique, without influencing the expression of Fas expression.

339 OXYGEN CONCENTRATION DURING IN VITRO MATURATION OF MURINE OOCYTES INFLUENCES SUBSEQUENT FETAL AND PLACENTAL OUTCOMES

Although the oxygen environment of the ovarian follicle is thought to influence oocyte developmental competence, little is known of the optimal oxygen environment for oocyte in vitro maturation (IVM). Previously, we found that oxygen concentration (either 2, 5, 10, or 20% O2; 6% CO2; and balance of N2) during IVM of murine oocytes had no effect on maturation rate or subsequent fertilization, cleavage, and blastocyst development rates. However, 2% O2 results in blastocysts with a higher (P &amp;lt; 0.05) trophectoderm cell number (mean � SEM, 35.1 � 2.3) when compared to 20% (19.4 � 1.7), with 5 and 10% O2 yielding similar but intermediate cell numbers. When examined for cell apoptosis by TUNEL labelling, the 2% O2 IVM-derived embryos were also found to have a significantly higher percentage of cells undergoing apoptosis compared to the 5% O2 IVM-derived embryos and embryos derived from in vivo matured oocytes (unpublished data). Although the blastocyst development rate is not affected by varying oxygen environment during oocyte maturation, the resultant blastocysts exhibited signs of differing quality. The aim of this study was to investigate the effect of varying oxygen during IVM on post-transfer outcomes. Immature cumulus-oocyte complexes (COCs) were collected from the ovaries of eCG-stimulated CBAB6F1 females (21 days) and cultured for 17–18 h under 2, 5, or 20% O2, whereas in vivo-matured COCs were also collected post-hCG. After IVF/C (both under 5% O2), 6 blastocysts were transferred to each uterine horn of pseudopregnant Swiss recipients. Fetal and placental parameters were measured on Day 18 of pregnancy. The ability of the embryos to implant or develop was not altered by IVM oxygen concentration. However, the average weight of fetuses derived from 5% O2 matured oocytes was reduced (823.3 � 28.1 mg, P &amp;lt; 0.05) compared to those in the 20% O2 group (928.5 � 26.1 mg). The average weight of the placenta in the 5% O2 group was also reduced (87.4 � 4.0 mg) compared to those derived from in vivo-matured oocytes (104.5 � 5.4 mg). In contrast, the fetal:placental weight ratio was unchanged in the 5% O2 treatment, suggesting these placentae, although small, are still efficient. This is the first evidence that programming of fetal/placental growth occurs from treatments applied during oocyte maturation.